Many Android users have Angry Birds loaded up on their handsets, and received notice of a new update available yesterday. Along with the content pushed with the update (30 new levels) came an unexpected notice – The app now requires access to your SMS messages.

Rovio responded in a message on Twitter, stating that it must be some mistake with the permission file that would get sorted on Monday. Today Rovio added an update to their blog, explaining why the SMS permissions are required.

Angry Birds requires SMS permission due to a new payment system implemented within the game – carrier billing. The payment is sent via SMS, and later charged to your phone bill. Rovio terms the new payment system “Bad Piggy Bank” and states the SMS permission will not be used for anything other than SMS payments.

The curious part about this change is that carrier billing is only available through one provider – Elisa in Finland. This leaves more than 99% of users exposing their SMS messages to Rovio with no particular reason. There was also no explanation during the update process, only via the blog after the update was rolled out. Rovio states that they are working with operators worldwide to make this in-app payment system accessible to more users.